An alkaline fuel cell use alkaline electrolytes to produce electricity. These fuel cells are clever pieces of technology that, like all other fuel cells, use electrochemistry to convert chemical energy into electrical energy. The fuel cell is composed of hot, concentrated Potassium Hydroxide surrounded by porous graphite electrodes. Hydrogen is introduced from one end and oxygen from the other; the resulting electrochemical reactions are then used to generate power. Fuel cells have the advantage that they form very less pollutants and generate a lot of power for a long duration on a fixed amount of ‘fuel’. The article below discusses alkaline fuel cell electrolytes.
Comparing Electrolytes: Potassium Hydroxide and Sodium Hydroxide
A fuel cell requires, as part of its design, a strong alkali that can circulate ions between the cathode and anode. This ensures continued electrochemical activity and uninterrupted power production. As a general rule, sodium hydroxide, although usable, is not preferred as an electrolyte. This is because the waste materials that do form in a fuel cell are less soluble in sodium hydroxide as compared to potassium hydroxide. Due to this difference in solubility, the former electrolyte is inefficient as a cleaner while the latter effectively mops up build up of by products that would otherwise hinder electrochemical activity.
Advantages of Alkaline Fuel Cells
As oxygen is involved in the electricity production process, an alkaline environment boosts efficiency due to its ability to circulate oxygen better as compared to acidic electrolytes. These fuel cells, as a result of alkaline electrolyte, work better at room temperature, to produce high current densities with less voltage drop. In addition to these advantages, alkaline fuel cells are cheaper to make than other cells due to fact that the cell and electrodes are made from low cost materials. These fuel cells have a high operating time – more than 15000 hours – because of the properties of the electrolyte such as the lack of corrosion it induces on the electrodes and easy removability of wastes. These factors coupled with a few others make alkaline fuel cells very cost effective. Fuel cells, in order to work at optimum efficiency, require a catalyst in the electrolyte that speeds up the concerned reactions. Cost effectiveness and reliability depend on the number of alternate catalysts present for the type of fuel cell. In the case of alkaline fuel cells, the number of alternate catalysts is very high - higher than the number of catalysts available for acid electrolyte fuel cells for instance.
Disadvantages of Alkaline Fuel Cells
Alkaline fuel cells have the disadvantage that they need to be installed in a carbon dioxide free environment. This is to avoid poisoning of the electrolyte. If carbon dioxide comes into contact with the alkaline environment, carbonates are formed. These carbonates are insoluble salts that clog the porous electrodes and block the flow of hydrogen and oxygen, resulting in power failure. To prevent such an event form occurring, the input gasses need to be purified extremely well. Although the technology for purification is fully developed and available, the process adds to the total cost of the fuel cell and makes it less practical.
Looking at the overall package, the advantages outweigh the disadvantages. The Alkaline fuel cell is a clever piece of technology that has practically been in use for a long time.